Theoretical and Empirical Analysis of Injection Mold Casting System Design.doc

Theoretical and Empirical Analysis of Injection Mold Casting System Design Tian Xuejun, School of General Education of Zhanjiang Normal University Abstract: Pouring system is one of the most important parts in injection craft and mould design. Based on the theoretical principle, this article will be related more to the experience to discuss the design of common pouring system. It mainly analyses the theory of plastic flow in runner and states the design of main runner，sub-runner and in-gate. Key words: Pouring mould、Runner、Experience based design Introduction: In the injection process and mold design, the gating system is a very important part, and it is related to the plastic properties, shapes and sizes of plastic parts, mold structures and injection processes and other factors. An unreasonable gating system will result in incomplete filling of plastic parts, brittle broken plastic parts, poor welding lines, shrinkage cavity, white spot, charring, warping and a series of other quality defects. At present, there are many forms of gating system of injection mold, which can be classified into common gating system and non-runner casting system on the whole. In this paper, the design of a common gating system is analyzed based on relevant theories, combined with more practical experience. A common casting system consists of main runner, branch runner and gate. Ⅰ. Theoretical analysis of the design In the injection process, the molten plastic as a fluid flows into a cavity through the gating system. We can analyze it by use of the theory of fluid mechanics. When plastic flows in the casting system, its Reynolds number is (Ρ and η are the melt density and viscosity respectively.υis velocity and L is the flowing length) Plastic viscosity coefficient, density and others are related to temperature, but the Reynolds number of all kinds of injection plastics Re = 0.05 ~ 0.005 can be obtained according toρ, υ, L, η empirical data in the injection process. Clearly, the Reynolds